Booty Sloshing 

The water left over on the seat from the water ride before yours

The booty sloshing on Splash Mountain was enough to get the full experience of the ride without all the drops.

Booty Sloshing by asgardiancapes March 2, 2016

Sloshing in her boots 

Said of a female, "sloshing in their boots" or "sloshing in her boots" refers to a state of sexual attraction or arousal so extreme that they're "wet" (i.e., vaginally lubricated) all the way down to their feet.

"Did you see that selfie of Angela Merkel with that handsome stud Syrian migrant? The old bag was sloshing in her boots!"

Sloshing in her boots by Honeyko November 2, 2015